The need to transmit high frequency digital signals has arisen with the digitization and increasing speed of electronic devices. Radiated noise not only from external interfaces and transmission cables between boards in a device but also from wiring between IC chips on the same board has thus become a significant problem.
A differential transmission system is widely used as a countermeasure to this radiated noise, although with a differential transmission system, the wirings of transmission paths intersect due to the terminal arrangement of the IC chips, resulting in distortion of characteristic impedance. If appropriate wiring that does not intersect is to be performed, IC chips having the same function but different terminal arrangements will thus be required.
In Japanese Patent Laid-Open No. 2007-149805, the configuration of a printed wiring board that maintains isometricity and reduces distortion of characteristic impedance even in the case where wirings for performing differential transmission intersect is disclosed.
In Japanese Patent Laid-Open No. 2003-249904, an integrated circuit having a shield effect that protects transmission signals from electromagnetic interference by enclosing connection balls with the power supply and GND is disclosed.
In Japanese Patent Laid-Open No. 11-186674, a technique that prevents loss of signal quality and radiation of noise by arranging a pair of data transmission circuits axisymmetrically on the board of a differential transmission circuit is disclosed.